1. Field of the Invention
The present invention relates in general to marine outdrives of the type used to propel small boats through the water, and more particularly to a marine outdrive apparatus for use with a gasoline powered motor of the type commonly found on lawnmowers.
2. Prior Art
Lawnmowers are a common household appliance utilized in many homes. The motors to power lawnmowers are plentiful and inexpensive. The purpose of this invention is to allow convenient conversion of a vertical shaft lawnmower motor into a marine outboard motor.
Prior art includes U.S. Pat. No. 5,405,277 for adaptation of a line trimmer into a boat motor. The ""277 patent is for utilization of the louder, lower power and more polluting two-stroke line trimmer engines. These types of engines are not permitted in environmentally sensitive areas. The small displacement line trimmer engines of the ""277 patent also tend to run at speeds far higher than would be optimal for use in the marine environment. To permit efficient use, the smaller two-stroke engines need a costly gear reduction. Smaller two stroke engines generally run at 6,500-7,500 RPM, far above the desirable RPM for normal boat propulsion. Without the addition of a gear reduction, the result is that there are dangerous loads placed on drive components leading to excessive wear and component failure.
U.S. Pat. No. 4,976,637 for conversion of a line trimmer to an outboard motor; and an adapter plate. The ""637 patent also provides for use of the less desirable high RPM two-stroke engines with many of the same faults as the ""277 patent.
U.S. Pat. No. 5,643,024 allows for the attachment of a four cycle internal combustion vertical shaft motor to an outdrive marine unit. Most pre-existing vertical shafts for use with outdrive motors are right hand rotation. Most small engines such as those used in lawnmowers are left hand rotation, making a simple adapter plate unsuitable for use with the majority of small displacement engines available. In addition, most outboard marine units are geared to an engine RPM range of 4,000 to 5,500 making the outdrive component undesirable for use with small engines of the lawnmower type which generally operate in the 2,400 to 2,800 RPM range.
The prior art is for the use of low power two-stroke engines commonly found in line trimmers, which are highly polluting and prohibited in many areas. The adapter plate disclosed requires that a vertical shaft element of a traditional marine motor be used, often being heavier than necessary and missing elements for optimal use with a lawnmower type engine.
As can be seen a need exists for a single outdrive assembly for use with readily available small four stroke engines of the 3 to 6xc2xd horsepower range. Such invention is below described and claimed.
Briefly, there is provided with the present invention a new and improved apparatus to convert a lawnmower motor to an outboard motor.
In the preferred embodiment, preferably a 3 to 6xc2xd horsepower vertical shaft lawnmower motor is attached to a tubular drive housing. The vertical shaft of the motor is attached by an adapter collet to a vertical drive shaft that resides in the housing. This is facilitated by industry standards for this type of vertical shaft engine. The Society of Automotive Engineers (SAE) has issued standards for two and four stroke vertical shaft engines of 6 horsepower and under, commonly known as the SAE j609 standard. This standard provides a uniform mounting of the drive shaft housing and drive shaft of the invention for the majority of engines suitable for use with the invention. The ready adaptability of this standard to the present invention should not be considered limiting, but simply demonstrative of the high degree of utility.
The upper end of the drive housing is preferably a bell type housing. This permits the ready mounting of small displacement engines with an extended motor shaft similar to the SAE j609 standard. The available space also permits the accommodation of protrusions on the mounting face of many engines, such as oil pan plugs, and the room to incorporate a centrifugal clutch with the adapter collet coupling the motor shaft to the drive shaft.
At the lower end of the drive housing is attached the gear carrier, propeller shaft and propeller. A lower opening in the housing is open at approximately a 90 degree angle from the drive shaft. In the preferred embodiment this opening is a non-circular ovoid. The gear carrier is also of an ovoid design, which provides for automatic alignment of the drive shaft to the gear carrier and propeller.
Displaced along the trailing edge of the drive housing is a skeg or rudder flange, and located at the end proximate the engine mount is a tiller for ease in providing directional control.
The use of standard four-cycle vertical shaft engines is particularly advantageous, as they are environmentally superior to two-stroke engines commonly found on smaller outboard drives and smaller engines of the line trimmer and chainsaw variety. Four-cycle engines do not burn and eject oil into the environment at the levels of two-stroke engines. Small vertical shaft four-cycle engines are also more commonly and readily equipped with mufflers reducing noise pollution.
Other elements provided to facilitate use include a transom mount and drive mount with a supporting saddle.
Due to the nature of the invention, traditional metal materials may be used to fabricate the components, or in the alternative the drive housing and significant other components may be made from synthetic materials such as plastic formed in an injection mold, saving production costs and time.
With the simplicity of limited number of parts, end users will be able to assemble, repair and maintain the invention with minimal skill, making the device lower in cost to maintain.
Accordingly, the objects and advantages of the present invention include: to provide an adapter that will allow for an alternative use of readily available inexpensive lawnmower motors; to provide an outboard motor device which can be an economic alternative to the purchase of an outboard motor; to provide a low cost alternative to two stroke marine outboard motors; to provide a low cost environmentally superior low power outboard drive; and to provide an outboard motor device that is light and easy to manage and maintain.